Several systems and methods exist for winding various types of tape. In computer and audio/visual systems, data storage systems are provided to read data from and/or write data to data storage media, such as magnetic tape. The data storage systems utilizing magnetic tape data storage media typically contain sophisticated data processing equipment and mechanical assemblies which usually include a drive unit for winding the tape.
Current tape winding systems use one or more spindles around which the tape is wound. To move tape in such systems, a drive system turns the first spindle in a first direction, thereby winding the tape from the first spindle onto the second spindle. By using the drive unit to turn the second spindle in an opposite direction, the tape may be wound from the second spindle to the first spindle.
For portability and tape storage purposes, it is often desirable to remove the tape from the system (hereinafter the "machine") which reads from and/or writes to the tape. Typically, the tape may either be housed entirely within a cassette, which has at least two spindles (the tape being attached at each end to a respective spindle), or within a cartridge which has one spindle to which one end of the tape is attached.
In the latter design, the second end of the tape may be removed from the cartridge and drawn inside the machine, where the second end of the tape is wound around a second spindle. When desired, the tape may be wound back inside the spindle within the cartridge, and the cartridge may then be removed from the machine. The latter (single-spindle) cartridge design has a significant advantage over cartridge designs employing two or more spindles. Specifically, cartridges having only one spindle are much more space efficient. For example, if the cartridge is square-shaped, tape wound within the single-spindle cartridge employs significantly more space within the cartridge than tape wound within multiple-spindle cartridges, where a great amount of cartridge space is left unused. However, since one end of the tape within a single-spindle cartridge is commonly removed from the cartridge, drawn into the machine, and wound around a spindle within the machine, problems arise in the design of an element or assembly which permits the machine to "grab" or "pick" and manipulate the tape end. A number of designs are well known in the industry, but each brings with it one or more deficiencies. Each design performs the same basic function (i.e., provides an element or assembly to which the machine may attached in order to grab or pick the tape end from the cartridge, thereby allowing the machine to pull the tape end inside of the machine and secure the tape end to a spindle within the machine). For purposes of this discussion, the machine mechanism which "picks" the tape end from the cartridge will hereinafter be called the "picker."
In one cartridge design, the tape end to be drawn inside the machine is secured to an element called a leader block. One example of this cartridge design is a cartridge made by IBM and designated Model 3480. When this cartridge is not being used, the leader block forms part of the cartridge wall itself (e.g., part of a perimeter wall or a corner of the cartridge). With the cartridge installed within it, the machine inserts the picker into a hole within the leader block. The picker then pulls the leader block into the machine from its position on the cartridge. The tape is secured to the leader block by being wrapped around a pin which is snap-fitted into a groove in the leader block. The pin is usually made of an elastomeric material, and is slightly larger than the groove into which it fits, so that the tape is firmly secured between the pin and the groove when the pin is snapped into place within the groove. The leader block shape of this cartridge design is also important in that once the leader block is fully drawn into the machine, one edge of the leader block forms an exterior surface of the spindle within the machine. Therefore, this leader block edge is curved to match the round exterior shape of the spindle.
A significant disadvantage of the leader block design is its size and shape. For a machine to read from or write to tapes stored within a cartridge using a leader block tape connection, the machine must have a picker which is compatible with the rather unusual design, size, and shape of the leader block. Specifically, the picker must fit within the hole in the leader block, while the internal mechanism of the machine must be designed to accept and secure the leader block (and its particular shape) within the machine. For the above-described leader block design, this means that the machine spindle must be designed to integrally house the leader block. These constraints dictate a relatively large leader block size, and require fairly specific machine and spindle design parameters to allow the leader block to be manipulated, moved, and secured inside the machine. A relative large leader block results in either a larger cartridge, a larger machine, or both.
In another cartridge design, a tape splice is used rather than a leader block. Such a cartridge design is employed in Digital Linear Tape cartridges manufactured by Quantum Corporation. In this design, a piece of stiff and resilient connector tape (e.g., mylar) is secured to the end of the tape within the cartridge. The opposite end of the connector tape is formed to be releasably attached to the picker, which is also a stiff and resilient piece of connector tape. The piece of connector tape secured to the tape within the cartridge may have a large hole in its free end, which is "grabbed" and pulled by a hook in the picker. The tape splice cartridge design addresses the problems inherent to the leader block tape connection design: the relatively large sized and unusually-shaped connection between the tape and picker. In the connector tape cartridge design, the spliced mylar-to-tape connection may be wound around the machine spindle, with the tape being wound on the machine spindle over the mylar-to-tape connection.
However, the tape splice cartridge design has its own design deficiencies. For example, reliability problems exist in the design of the stiff and resilient connection tape used to connect the picker to the cartridge tape. The connection tape must be stiff enough to resist bending during the connecting procedure (when the machine connects the connector tape to the cartridge tape), but must be flexible enough to easily bend while being wound around a spindle. Therefore, a compromise must be made to either stiffen the connection tape (thereby making winding more difficult and increasing the chance of incorrectly-wound tape) to facilitate easier "picking", or relax the connector tape (thereby making the picking procedure more difficult or unreliable). This compromise can result in a connection or winding which is undesirable. For example, incorrectly-wound tape may lead to tape damage and/or misfeeding of the tape in the cartridge or in the machine. Also, when a desired connection is not made and the machine attempts to wind the tape into the machine, the machine can "swallow" the picker (the disconnected connector tape). When is thus "swallowed" into the machine, the machine usually must be serviced to extract the picker from the machine. Conversely, when a desired disconnection procedure fails, attempts to release the cartridge from the machine can cause to damage to the tape, the cartridge, and/or the machine. In short, the compromise necessary to provide a connector tape which is both stiff enough to facilitate reliable connections and disconnections while being relaxed enough to be properly wound results in a less-than-optimal design.
The tape splice cartridge design has other undesirable features. For example, when the tape is wound around a spindle, the mylar-to-tape connection may cause the wound tape above the mylar-to-tape connection to be thicker than the other areas along the circumference of the wound tape (creating a "bump" in the wound tape). This bump caused by the mylar-to-tape connection is amplified as more tape is wound on the spindle, and has an undesirable effect of creating a "once-around" type of runout on the spindle which can distort a recorded signal on the tape. Another disadvantage of the tape splice cartridge design is that during winding operations, the mylar-to-splice connection passes over the recording head(s) of the machine. This action exposes the recording head to potential damage and/or excessive wear.
As described above, although designs exist for connecting the tape of a cartridge to the picker of the machine, each design suffers from significant drawbacks, including inefficient connection size, connection elements which create difficulty in establishing compatibility between cartridges and machines, and connection elements which are not optimally designed for both winding and connecting operations. Therefore, a need exists for a tape-to-machine connection which is space efficient (is as small as possible), affords compatibility with a number of different machines into which a cartridge may be inserted (preferably without design changes to the machines), and has a simple connection design for dependable connection and disconnection operations.
A tape-to-machine connection that overcomes many of the disadvantages of known designs is described in copending U.S. patent application Ser. No. 09/055,016, filed Apr. 3, 1998, titled "Tape Leader Pin Assembly and Method for Making the Same". This application describes a leader pin assembly and a method of making a leader pin assembly for use in connecting tape with elements of a machine which manipulate the tape (e.g., move the tape, wind or unwind the tape from a spindle). In one preferred embodiment, the leader pin assembly includes three parts. The first part is a leader pin with an elongated "barbell" shape. At least one pair of flanges flanks a center section of the leader pin around which the tape is wrapped. The second part is an flexible element which is fitted over the tape wrapped around the center section of the leader pin. The third part is a clip fitted around the flexible element to secure the flexible element in a snug position around the tape and leader pin.
In another preferred embodiment, the flexible element and the clip are unitary, either constituting one element or being attached to one another. In other preferred embodiments, the entire leader pin assembly is molded in place around the tape, or the tape is attached to a surface of the leader pin assembly by a bonding material or other fastener.
In those embodiments employing a clip, the flexible element is held in place by a C-shaped spring clamp having an inner diameter slightly smaller than the outer diameter of the flexible element. The clamp, whether over or in conjunction with the flexible element, is snapped into place over the tape wound around the center section of the leader pin.
As recognized in Ser. No. 09/055,016, this arrangement presents several inherent problems. For example, the spring-fit nature of the clip can result in deformation of the flexible element and uneven clamp force on the tape. Deformation of the flexible element may require removal of material from the flexible element to maintain concentricity. Furthermore, proper operation of the cartridge requires for the clamp to retain the tape such that the tape can withstand a linear force (in a direction pulling the tape away from the leader pin assembly) of 16 Newtons without permitting any tape slippage. Recent tests have determined that this standard is not being met by current clamping structure and methods.
It is apparent from the foregoing that the need exists for a tape leader pin clamp and method for securing the clamp to a leader pin assembly that will minimize deleterious deformation of the flexible element while maintaining adequate and uniform force to retain the tape on the leader pin.